Capacitor and method of manufacturing the same

ABSTRACT

A capacitor and a method of manufacturing the same are disclosed. The BST dielectric film is disposed between the lower electrode by coating a sidewall of the upper electrode and then forming the lower electrode in a second contact hole defined by the upper electrode and BST film. As such, degradation in the step coverage characteristic caused by forming a BST dielectric film having a desired composition ratio is avoided.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates generally to a capacitor and a method ofmanufacturing the same. More particularly, the disclosed to a capacitorand a method of manufacturing the same, which can improve the stepcoverage of a BST dielectric film formed by a MOCVD method and that canprevent a change in the composition ratio to improve the dielectriccharacteristic of a capacitor.

[0003] 2. Description of the Prior Art

[0004] The use of a high dielectric BST thin film as a capacitormaterial for Giga DRAMs has been studied. In a device having the cellsize of less than 0.10 μm², even though the BST thin film is used as adielectric material, a lower electrode must be formed in athree-dimensional structure or a capacitor must be formed with a concavestructure. At this time, if the structure is etched using a noble metalsuch as Pt, Ru, Ir, etc. in order to form a lower electrode, the upperportion of the lower electrode is not etched with a profile of 90° C. Itis at most etched with a profile of about 80° C. Therefore, it isimpossible to use this method in a cell of that is smaller than 0.10μm².

[0005] As a result, in order to solve this problem, a capacitor with aconcave structure must be manufactured. At this time, in order to formsuch an electrode and a dielectric film, it is necessary that the CVDmethod have good step coverage. However, the types of precursors for thePt CVD being developed now have been limited and they are alsoexpensive. Therefore, it is economical to use a Ru precursor due to itslower cost. The capacitor manufactured thus is mainly used to store datain a DRAM.

[0006]FIG. 1 is a cross-sectional view for explaining a method ofmanufacturing a conventional capacitor. A first insulating film 2 isformed on a semiconductor substrate 1 in which various components forforming a semiconductor device are formed. Then, a contact hole isformed so that a given junction can be exposed. Next, a polysiliconlayer for contact plug 3 is formed within the contact hole and is thenflatten by chemical mechanical polish process, thus forming a Si₃N₄ film6 and a second insulating film 7 on the entire structure.

[0007] Thereafter, a given region of the second an insulating film 7 isetched to form an opening wider than the contact hole, while exposingthe polysilicon plug 3. Then, barrier layers 4 and 5, and a Ru lowerelectrode 8 are formed at the sidewall and at the bottom of the opening.Next, a BST dielectric film 9 and an upper electrode 10 are formed onthe entire structure thereby covering the Ru lower electrode 8.

[0008] Conventionally, with a method of manufacturing a capacitor havinga concave structure, the area of the lower electrode occupies less than10% of the total wafer area. In other words, seeing the surface of thewafer before a MOCVD BST dielectric film is formed, most of the surfaceis a SiO₂ film being an insulating layer and the lower electrodeoccupies a very small area.

[0009] However, the BST dielectric film is made of 4-element series suchas Ba, St, Ti and O₂, and if it is formed by CVD method, the compositionratio of a thin film is different depending on the condition of anunderlying substrate. Also, in a capacitor of a concave structure or astacked structure, as the cell size of the BST dielectric film isreduced even though it is deposited by a CVD method, the aspect ratiobecomes relatively larger, thus significantly degrading the stepcoverage characteristic.

[0010] In a conventional concave structure, the step coverage after theMOCVD BST dielectric film is deposited is at most about 50%, whichsignificantly makes it difficult to manufacture a capacitor structure ina capacitor having the cell size of 0.1 μm². That is, in case of aconcave structure, as BST of a vapor state, made of 4-element seriessuch as Ba, St, Ti and O₂ enters holes to form a BST dielectric film, apoor step coverage results in comparison to TiN or other thin films.Even in the case that the lower electrode has a stack structure, as mostof the wafer is a SiO₂ film and an electrode occupies a very small area,the step coverage due to the difference of temperature is poor. Further,in case that the composition ratio of the BST dielectric film isdifferent, it may have a critical affect on the electricalcharacteristics of a capacitor.

[0011] However, in the case that a lower electrode of a conventionalcapacitor is formed, if a MOCVD BST dielectric film is to be formed, thecomposition ratio of a BST dielectric film deposited on a SiO₂ and a BSTdielectric film deposited on a lower electrode will be different. Also,as the composition ration of the BST dielectric film deposited on thelower electrode is different from that expected, a capacitor having agood electrical property cannot be obtained. Thus, in order to form aBST dielectric film having a desired composition ratio, the processtemperature must be increased. In that case, a TiN/Ti film used as adiffusion barrier layer is oxidized, and particles are inevitablygenerated during the process of forming a BST dielectric film.

SUMMARY OF THE DISCLOSURE

[0012] A capacitor and method of manufacturing the same are disclosed,which can improve the step coverage of a BST dielectric film and improvethe electrical characteristics of the capacitor by making itscomposition ratio constant, in such a way that the upper electrode isformed at a position so that a SiO₂ film remains in a conventional lowerelectrode structure. And, a BST dielectric film is formed between theupper electrode and the lower electrode without contacting the SiO₂film.

[0013] One disclosed method of manufacturing a capacitor ischaracterized in that it comprises the steps of providing asemiconductor substrate in which a first insulating film through which ajunction is open by a contact hole is formed, forming a contact plugwithin the contact hole, sequentially forming a Si₃N₄ film and a secondinsulating film on the entire structure, etching the second insulatingfilm by etching process using an upper electrode mask to form anopening, forming an upper electrode within the opening, removing thesecond insulating film and then forming a BST dielectric film at thesidewall of the upper electrode, removing the Si₃N₄ film on the contactplug, and forming noble metals for a lower electrode on the entirestructure and then performing a chemical mechanical polish process toform a lower electrode.

[0014] In the above method, the contact plug is formed using a plugmethod by which TiN is covered in a TiN/TiSi/Poly-Si structure.Two-element nitride-series materials or three-element nitride-seriesmaterials such as TiSiN, TiAlN are used instead of a diffusion barrierlayer of a TiN film and a TiN film.

[0015] The Si₃N₄ film is formed with a thickness of about 500 Å.

[0016] The second insulating film is formed with a thickness rangingfrom about 5000 Å to about 15000 ÅA.

[0017] The upper electrode and the lower electrode are formed with athickness ranging from about 5000 Å using noble metals such as Pt, Ru,RuOx, Ir and IrOx by means of a CVD method.

[0018] The BST dielectric film is formed with a thickness ranging fromabout 150 Å to about 300 Å by a CVD method. After the BST dielectricfilm is formed, a RTA process is performed at a temperature ranging fromabout 700° C. to about 800° C. under a nitrogen atmosphere or a vacuumto crystallize the BST dielectric film. After the BST dielectric film isformed, a RTA process is performed under an oxygen atmosphere at atemperature ranging from about 350° C. to about 550° C. or a N₂O plasmaprocess or an ultraviolet ozone UV-O₃ process is carried out tocompensate for oxygen loss within said BST dielectric film.

[0019] A capacitor is characterized in that it comprises a firstinsulating film formed on a substrate, a contact plug formed within thefirst insulating film, an upper electrode formed on the first insulatingfilm, a dielectric film formed sidewall the upper electrode, and a lowerelectrode formed on the contact plug.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The aforementioned aspects and other features of the disclosedmethods will be explained in the following description, taken inconjunction with the accompanying drawings, wherein:

[0021]FIG. 1 is a cross-sectional view illustrating a prior art methodof manufacturing a conventional capacitor; and

[0022]FIGS. 2A through 2F are cross-sectional views illustrating adisclosed method of manufacturing a capacitor.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0023] The disclosed methods will be described in detail with referenceto accompanying drawings. FIGS. 2A to 2F are cross-sectional views forexplaining the disclose method of manufacturing a capacitor.

[0024] Referring now to FIG. 2A, after a first insulating film 22 isformed on a semiconductor substrate 21 in which various components forforming a semiconductor device are formed, a contact hole is formed sothat a junction can be exposed. Then, contact plugs 23 through 25 areformed within the contact hole using TiN capped plug method withTiN/TiSi/Poly-Si.

[0025] The TiN capped plug method with TiN/TiSi/Poly-Si will be nowexplained. First, a polysilicon layer 23 is formed to fill a portion ofa contact hole. Then, after Ti is formed on the polysilicon layer 23, itis exposed to a thermal process to form a TiSi film 24. Then, unreactedTi is removed and a portion of the contact hole is again coated. Next, aTiN film 25 is formed at the remaining portions of the contact hole tocompletely fill the contact hole. As such, after the contact plugs 23through 25 are formed, the surface of the first insulating film 22 isflattened by chemical mechanical polish process. The TiSi film and theTiN 24 and 25 are diffusion barrier layers for preventing reaction withthe lower electrode to be formed by a subsequent process. The diffusionbarrier layers 24 and 25 may be formed of two-element nitride-seriesmaterials or three-element nitride-series materials such as TiSiN,TiAlN, etc. for increasing oxidization resistance.

[0026] Referring now to FIG. 2B, a Si₃N₄ film 26 and a second insulatingfilm 27 are sequentially formed on the first insulating film 22including the TiN film 25. Then, the second insulating film 27 is etchedusing an upper electrode mask to form an opening.

[0027] The Si₃N₄ film 26 is formed with a thickness of about 500 Å,which prevents a lower layer when the second insulating film 27 isetched during a subsequent process. The second insulating film 27 isformed in thickness ranging from about 5000 Å to about 15000 Å.

[0028] Referring now to FIG. 2C, an upper electrode 28 is formed withinthe opening by means of a CVD method.

[0029] The upper electrode 28 is formed, in such a way that it is formedon the entire structure including the second insulating film 27 usingnoble metals having a large work function such as Pt, Ru, RuOx, Ir andIrOx, etc. and each of the noble metals for an upper electrode on thesecond insulating film 27 are then partially removed by etch-backprocess or chemical mechanical polish process. The height of the upperelectrode 28 must be more than about 5000 Å and can achieve a desiredcapacitance for a cell size of 0.1 μm². If the upper electrode is formedwithout first forming the second insulating film and then etching thesecond insulating film, for a cell size of 0.1 μm², the upper portion ofthe noble metals will be slanted when the noble metals for the upperelectrode are etched. In order to overcome this problem, after a SiO₂film 27 having a vertical etch profile is formed and is then etched, ifthe upper electrode 28 is formed, an upper electrode 28 having almostvertical shape can be obtained.

[0030] Referring now to FIG. 2D, the second insulating film 27 betweenthe upper electrodes 28 is removed.

[0031] Referring now to FIG. 2E, a BST film is formed on the entirestructure including the upper electrodes 28 by means of CVD method.Then, in order to crystallize the BST film, a RTA process is performed.In order to compensate for oxygen escaped during the process ofcrystallizing the BST film, a rapid temperature annealing (RTA) processis performed. Thereafter, the BST film remains only at the sidewalls ofthe upper electrodes 28 by an anisotropy etch process, thus forming aBST dielectric film 29.

[0032] The RTA process for crystallizing the BST film is performed undernitrogen atmosphere at a temperature ranging from about 700° C. to about800° C. The crystallization process of the BST film may be performedafter the BST film on the upper electrodes 28 is removed. The RTAprocess for compensating for oxygen loss within the BST film may beperformed under an oxygen atmosphere at a temperature ranging from about350° C. to about 550° C. or may be performed by a N₂O plasma process orultraviolet ozone UV-O₃ process. The BST dielectric film 29 is formedwith a thickness ranging from about 150 Å to about 300 Å. The RTAprocess for compensating for oxygen within the BST film may be performedafter the BST film on the upper electrodes 28 is removed.

[0033] Referring now to FIG. 2F, after the Si₃N₄ film 26 on the TiN film25 is etched, a lower electrode 30 is formed.

[0034] The lower electrode 30 is formed in such a manner that the noblemetals such as Pt, Ru, RuOx, Ir and IrOx, etc., which constitute theupper electrode 28, are formed on the entire structure and each of thenoble metals on the upper electrode 28 and the BST dielectric film 29are then removed. After the lower electrode 30 is formed, the RTAprocess for compensating for oxygen within the BST dielectric film 29may be performed.

[0035] In the disclosed method, in order to solve the step coverage andcomposition problems in the BST dielectric film 29, the portion of theSiO₂ film 27 remaining in the conventional structure is replaced by anupper electrode 28 of the capacitor. This process technology can solvethe problem that the composition of the CVD BST dielectric film ischanged since most of the wafer is covered with electrode materials.Also, it can reduce generation of particles since it can adjust thecomposition of a thin film even the BST film is formed at a lowtemperature by a CVD method. As the capacitor is formed by the disclosedmethod, the step coverage problem is solved. That is, as the capacitorstructure is not in a hole shape but a stacked structure, and most ofthe wafer surface on which a BST film is deposited is covered withelectrode materials unlike the conventional stacked structure. As aresult, the BST film can be uniformly formed since there is notemperature differential across the wafer surface.

[0036] As mentioned above, the disclosed method can improve the stepcoverage characteristic by making the structure of a capacitordifferent. The disclosed method can also improve an electriccharacteristic of a capacitor since it can make a desired composition ofa BST dielectric film.

[0037] The disclosed method has been described with reference toparticular embodiments in connection with particular applications. Thosehaving ordinary skill in the art and access to the teachings of thedisclosed method will recognize additional modifications andapplications within the scope thereof.

[0038] It is therefore intended by the appended claims to cover any andall such applications, modifications, and embodiments within the scopeof the disclosed method.

What is claimed:
 1. A method of manufacturing a capacitor, comprisingthe steps of: providing a semiconductor substrate; forming a firstinsulating film on the substrate having a contact hole; forming acontact plug within said contact hole; sequentially forming a Si₃N₄ filmand a second insulating film on the entire structure; etching saidsecond insulating film using an upper electrode mask to form an opening;forming an upper electrode within said opening; removing said secondinsulating film thereby exposing a sidewall of the upper electrode;forming a BST dielectric film on the sidewall of said upper electrode;removing said Si₃N₄ film on said contact plug; forming a layer of noblemetals on the entire structure; and performing a chemical mechanicalpolish process to form a lower electrode.
 2. The method of manufacturinga capacitor according to claim 1, wherein said contact plug comprises aTiN/TiSi/Poly-Silicon structure.
 3. The method of manufacturing acapacitor according to claim 1, wherein said contact plug comprisestwo-element nitride-series materials such as TiN film or three-elementnitride-series materials such as TiSiN film and TiAlN as a diffusionbarrier layer.
 4. The method of manufacturing a capacitor according toclaim 1, wherein said Si₃N₄ film is formed with a thickness of about 500Å.
 5. The method of manufacturing a capacitor according to claim 1,wherein said second insulating film is formed with a thickness rangingfrom about 5000 Å to about 15000 Å.
 6. The method of manufacturing acapacitor according to claim 1, wherein said upper electrode and saidlower electrode are formed in thickness of about 5000 Å using noblemetals selected from the group consisting of Pt, Ru, RuOx, Ir and IrOxby means of a CVD method.
 7. The method of manufacturing a capacitoraccording to claim 1, wherein said BST dielectric film is formed by aCVD method.
 8. The method of manufacturing a capacitor according toclaim 1, wherein after BST dielectric film is formed, a RTA process isperformed at a temperature ranging from about 700° C. to about 800° C.under a nitrogen atmosphere or under a vacuum atmosphere to crystallizesaid BST dielectric film.
 9. The method of manufacturing a capacitoraccording to claim 1, wherein after said BST dielectric film is formed,a RTA process is performed under an oxygen atmosphere at a temperatureranging from about 350° C. to about 550° C.
 10. The method ofmanufacturing a capacitor according to claim 1, wherein after said BSTdielectric film is formed, a N₂O plasma process is performed tocompensate for oxygen within said BST dielectric film.
 11. The method ofmanufacturing a capacitor according to claim 1, wherein after said BSTdielectric film is formed, an ultraviolet ozone process is performed tocompensate for oxygen within said BST dielectric film.
 12. The method ofmanufacturing a capacitor according to claim 1, wherein said BST adielectric film is formed with a thickness ranging from about 150 Å toabout 300 Å.
 13. A method of manufacturing a capacitor, comprising thesteps of: forming a first insulating film on a substrate; forming acontact hole in said first insulating film; forming a contact plugwithin said contact hole; forming a second insulating film on the entirestructure; patterning said second insulating film to form an opening onsaid first insulating film; forming an upper electrode within saidopening; forming a dielectric film on said upper electrode; and forminga lower electrode on said contact plug.
 14. The method of manufacturinga capacitor according to claim 13, further comprising the step ofremoving said second insulating film to expose said contact plug. 15.The method of manufacturing a capacitor according to claim 13, whereinsaid contact plug is comprised of forming a polysilicon layer in saidcontact hole and forming a diffusion barrier layer on said polysiliconlayer.
 16. The method of manufacturing a capacitor according to claim15, wherein said diffusion barrier layer is formed two-elementnitride-series materials such as TiN film or three-elementnitride-series materials such as TiSiN film and TiAlN.
 17. The method ofmanufacturing a capacitor according to claim 13, wherein said contactplug comprises a TiN/TiSi/Poly-Silicon structure.
 18. The method ofmanufacturing a capacitor according to claim 13, further comprising thestep of forming a Si₃N₄ film on the entire structure including saidcontact plug before forming said second insulating film.
 19. The methodof manufacturing a capacitor according to claim 18, wherein said Si₃N₄film is formed with a thickness of about 500 Å.
 20. The method ofmanufacturing a capacitor according to claim 13, wherein said upperelectrode and said lower electrode are formed of noble metals selectedfrom the group consisting of Pt, Ru, RuOx, Ir and IrOx.
 21. The methodof manufacturing a capacitor according to claim 13, wherein saiddielectric film is formed with a BST dielectric film.
 22. The method ofmanufacturing a capacitor according to claim 21, wherein after said BSTdielectric film is formed, a RTA process is performed at a temperatureranging from about 700° C. to about 800° C. under a nitrogen atmosphereor under a vacuum atmosphere to crystallize said BST dielectric film.23. The method of manufacturing a capacitor according to claim 21,wherein after said BST dielectric film is formed, a RTA process isperformed under an oxygen atmosphere at a temperature ranging from about350° C. to about 550° C.
 24. The method of manufacturing a capacitoraccording to claim 21, wherein after said BST dielectric film is formed,a N₂O plasma process is performed to compensate for oxygen within saidBST dielectric film.
 25. The method of manufacturing a capacitoraccording to claim 21, wherein after said BST dielectric film is formed,an ultraviolet ozone process is performed to compensate for oxygenwithin said BST dielectric film.
 26. The method of manufacturing acapacitor according to claim 21, wherein said BST a dielectric film isformed with a thickness ranging from about 150 Å to about 300 Å.
 27. Acapacitor comprising: a first insulating film formed on a substrate; acontact plug formed within said first insulating film; an upperelectrode formed on said first insulating film; a dielectric film formedsidewall said upper electrode; and a lower electrode formed on saidcontact plug.
 28. The capacitor according to claim 27, wherein saidcontact plug comprises a TiN/TiSi/Poly-Silicon structure.
 29. Thecapacitor according to claim 27, wherein said upper electrode and saidlower electrode are formed of noble metals selected from the groupconsisting of Pt, Ru, RuOx, Ir and IrOx.
 30. The capacitor according toclaim 27, wherein said dielectric film is formed with a BST dielectricfilm.